1. Field of the Invention
This invention relates to a BGA (Ball Grid Array) type semiconductor device which has ball-shaped conductive terminals.
2. Description of the Related Art
A CSP (Chip Size Package) receives attention in recent years as a three-dimensional mounting technology as well as a new packaging technology. The CSP is a small package having about the same outside dimensions as those of a semiconductor die.
A BGA type semiconductor device has been known as a kind of CSP. A plurality of ball-shaped conductive terminals made of a metal such as solder is arrayed in a grid pattern on one principal surface of the BGA type semiconductor device and is electrically connected with the semiconductor die mounted on the other side of the package.
When the BGA type semiconductor device is mounted into electronic equipment, the semiconductor die and an external circuit on a printed circuit board are electrically connected by compression bonding of each of the conductive terminals to each of wiring patterns on the printed circuit board.
Such a BGA type semiconductor device has advantages in providing a large number of conductive terminals and in size reduction over other CSP type semiconductor devices such as an SOP (Small Outline Package) and a QFP (Quad Flat Package), which have lead pins protruding from their sides. The BGA type semiconductor device can be used, for example, as an image sensor chip for a digital camera incorporated into a mobile telephone.
FIG. 22A and FIG. 22B show an outline structure of a conventional BGA type semiconductor device. FIG. 22A is an oblique perspective figure of front side of the BGA type semiconductor device. And FIG. 22B is an oblique perspective figure of a back side of the BGA type semiconductor device.
A semiconductor die 104 is sealed between a first glass substrate 102 and a second glass substrate 103 through epoxy resins 105 and 105 in the BGA type semiconductor device. A plurality of ball-shaped terminals 106 is arrayed in a grid pattern on a principal surface of the second glass substrate 103, that is, on the back side of the BGA type semiconductor device 101.
The conductive terminals 106 are connected to the semiconductor die 104 through second wirings 110. The second wirings 110 is connected with aluminum wirings pulled out from inside of the semiconductor die 104, making each of the ball-shaped terminals 106 electrically connected with the semiconductor die 104.
Detailed explanation on a cross-sectional structure of the BGA type semiconductor device 101 will be given referring to FIG. 21. FIG. 21 shows a cross-sectional view of the BGA type semiconductor devices 101 divided along dicing lines into individual dice.
A first wiring 107 is provided on an insulation film 108 on a surface of the semiconductor die 104. The semiconductor die 104 is bonded on the first glass substrate 102 with the resin 105. A back side of the semiconductor die 104 is bonded on the second glass substrate 103 with the resin 105.
One end of the first wiring 107 is connected to the second wiring 110. The second wiring 110 extends from the end of the first wiring 107 to a surface of the second glass substrate 103. And the ball-shaped conductive terminal 106 is formed on the second wiring 110 extending onto the second glass substrate 103.
Next, a manufacturing process of the semiconductor device 101 will be explained in sequence, referring to FIG. 17 through FIG. 21.
A semiconductor wafer having a plurality of semiconductor dice 104 is provided and its surface is covered with an insulation film 108 made of insulating material such as SiO2, as shown in FIG. 17. Then the first wirings 107 are formed on the insulation film 108 across borders (dicing lines) S along which the plurality of semiconductor dice 104 is to be cut into individual dice. Line S represents borders between the semiconductor dice 104.
After that, the first glass substrate 102 to hold the semiconductor dice 104 is bonded on the surface of the semiconductor dice 104, on which the first wirings 107 are formed, with the transparent epoxy resin 105.
After back grinding the semiconductor dice 104 to reduce thickness of the dice, the back surface of each of the semiconductor dice 104 and the insulation film 108 are etched along the borders S to expose the first wirings 107.
After that, the etched semiconductor dice 104, side surfaces of the insulation film 108 and exposed portions of the first wirings 107 are covered by the epoxy resin 105, and the second glass substrate 103 is bonded on the back surface of each of the semiconductor dice 104 using the epoxy resin 105 as a binder, as shown in FIG. 18.
Next, the second glass substrate 103 is performed a V-shaped notching along each of the borders S, as shown in FIG. 19. The notching is a cutting process using a cutting tool such as a blade. A V-shaped groove formed by the notching in this process reaches the first substrate 102. With this process, the first wiring 107 is separated into two portions, and their side surfaces are exposed.
An aluminum layer is formed to cover the second glass substrate 103 and cut surface formed by the notching, as shown in FIG. 20. The exposed surface of the first wiring 107 and the aluminum layer are thus connected. After that, the aluminum layer is subject to patterning to make a predetermined wiring pattern and form the second wiring 110.
Next, a protection film 111 such as a solder mask is formed on the second wiring 110, as shown in FIG. 21. Then the ball-shaped conductive terminal 106 is formed on the second wiring 110 through an opening in the protection film 111. Dicing along the borders S follows. With this, the conventional BGA type semiconductor device 101 is completed.
However, there are following problems in the above BGA type semiconductor device 101 and its manufacturing process.
First, the manufacturing process is complicated and expensive, since two glass substrates 102, 103 are used in the manufacturing process of the conventional BGA type semiconductor device 101.
Second, the notching, a peculiar process, is required to cut the first wirings 107, because the second glass substrate 103 is bonded on the back surface of each of the semiconductor dice 104. The notching causes abnormalities on the cut surface at the edge of the first wiring 107, such as incorporation of foreign material or contamination.
Third, there is a possibility that the side surface of the first wiring 107 and the second wiring 110 are disconnected when external stress is applied, because a length of contact between the side surface of the first wiring 107 and the second wiring 110 is only 2 μm to 3 μm. In addition, the side surface of the first wiring 107 is rough and poorly adheres to the second wiring 110, because the side surface of the first wiring 107 is a cut surface formed by notching.
This invention is directed to solve the problems addressed above, and offers a BGA type semiconductor device 101 at a reduced cost. This invention also improves the connection between the first wiring 107 and the second wiring 110 and offers a BGA type semiconductor device 101 of high reliability.